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  1. duke37

    Linear position Sensor for tiny Hydraulic Cylinders

    Fix a magnet to the valve stem and measure the flux with a Hall effect sensor?
  2. duke37

    Please recommend instruments and help for circuit board troubleshooting.

    7. Transformer. For efficiency, the windings should be low resistance. You will need to find the normal resistance and see if you component is within say 5%. Shorted turns may not drop the resistance much. Say you short 10 turns in a 1000 turn winding, that is only 1% but could have a...
  3. duke37

    DC voltage regulator

    If the input voltage goes above the zener voltage, then the zener may be asked to dump a lot of current so a fuze before the zener should protect it. The zener is there to protect the regulator. The regulator is there to protect the gauge.
  4. duke37

    DC voltage regulator

    A 7812 regulator would do the job, it will do 1A. If the load takes 1A then the regulator will need to dissipate up to 8W so will need a heat sink. The main problem will be to protect the regulator from short term transients so I would suggest a 1A input fuse followed by a 20V zener to...
  5. duke37

    Looking for oscillator and frequency divider schematics

    I would not worry too much about the variation from 50% duty cycle. A 50% square wave has only odd harmonics and a sawtooth wave is preferred which has even and odd harmonics. Hammond made an organ with square wave generators but modified this by adding harmonics to give some even harmonics...
  6. duke37

    Trapezoidal Wave Generator Circuit

    The cross coupled bistable should be limited to about 6V supply so that the reverse e/b voltage is not exeeded. The circuit refered to in #28 runs on 12V but a diode is placed in series with the base of the first transistor to protect it.
  7. duke37

    Resistance Decade box

    The reason for limiting the number of decades is the accuracy of the resistors Consider changing from 99999.9 to 100000.0. Will the resistance go up or down?
  8. duke37

    PGA4311 bypass caps

    C12 is not necessarily closer to the digital ground, this is a circuit diagram, not a layout. Layout and capacitors will be critical to minimise digital interference on the analog signal. I presume p7 and p22 are internally connected. I think that any good capacitors would do.
  9. duke37

    PGA4311 bypass caps

    What is the problem? The capacitors should be connected from close to the chip to a good ground plane, there is a layout earlier in the document which I have not looked at.
  10. duke37

    Problem - Triangle Wave Generator

    To know the state that the amps are stuck in.
  11. duke37

    Looking for oscillator and frequency divider schematics

    Here is the heart of the Livingston Monarch. It uses pnp germanium alloy junction transistors and runs on -12V. Now, you should use npn transistors run on less than 6V, because of the limited base/emitter voltage. You will need a LOT of components to get a wide range instrument.
  12. duke37

    How long should antenna wire be to receive amateur band?

    A 20m halfwave dipole will be a wire or aluminium tubing 10m long. This should be split in the middle and connected to some feeder cable. 50 ohm or 75 ohm co-ax is often used and will be adequate for reception. Much more accurate construction and matching is necessary for transmission. The...
  13. duke37

    Need help with 12 volt charging system please

    If I remember correctly a 12V battery should be charged between 13.8 and 14.4V. The lower voltage would indicate that your generator is either set too low or is inadequate to supply the current.
  14. duke37

    DC to AC

    What voltage and power do you want? There are many circuits and chips depending on the application.
  15. duke37

    Looking for oscillator and frequency divider schematics

    Somewhere I have the circuit for a Livingston Monarch organ. I could look this up if you are interested. It uses germanium transistors. The top octave uses a pot core oscillator and the dividers are discrete components. Using dividers means that the octave frequencies are locked to each...
  16. duke37

    Looking for oscillator and frequency divider schematics

    As simple as possible does not agree with discrete components. The simplest oscillator that I know is a Schmitt trigger with a capacitor from input to ground and a resistor from output to input. The output will be square wave. A 4093 will give four oscillators and a 40106, six. I do not...
  17. duke37

    Wheel movement sensor / alarm

    The reason for using an AC relay is that the core is laminated so the Eddy current losses will be minimised. This is also the reason for removing the copper ring which is there to provide some phase change on half the pole piece to reduce vibration. I sorted out a shaft monitor on a combine...
  18. duke37

    70.7V line transformer

    In the UK, the PA system uses 100V line, perhaps this is peak and the same as 70.7V line. Valve amplifiers can produce a low output impedance with negative feedback so that the loading can be varied as required. The speakers are coupled to the line with transformers. These have multiple...
  19. duke37

    Geiger counter / radiation meter modification

    All radiation counters produce pulses. The Geiger counter produces pulses of fixed amplitude whereas a proportional counter will give puses depending on the radiation. Since pulses are detected you cannot get an instantaneous reading, you will need to integrate over a certain time. The way...
  20. duke37

    Wheel movement sensor / alarm

    The relay coil is a good idea, it should be used with its original core. The relay should be an AC type to get a laminated core and the copper ring should be removed. The magnet will be placed where the armature was. You may be able to use an AC solenoid also.
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